The present invention relates to the field of initiators, and more particularly to a pyrotechnic initiator having a center pin with a circumferential notch retention feature.
Pyrotechnic initiators have many uses in industrial and consumer applications. One important use is the inflation of airbags in motor vehicles. As airbag production has steadily increased, significant efforts have been made to reduce the cost of reliable airbag initiators. One advance has been the use of a pyrotechnic droplet that is dispensed onto the header of the airbag initiator in a liquid or slurry form. For example, a generally suitable formula and techniques for dispensing liquid or slurry pyrotechnic droplets are described in U.S. Pat. No. 5,821,446 to Chatley, Jr., and U.S. Pat. No. 5,939,660 to Fogle, Jr., which are incorporated herein by reference as if set forth in full. A droplet can be dispensed with volumetric dispensing syringe-type equipment, or it can also be sprayed or placed after it is dispensed onto another part of the equipment.
And as is shown in FIG. 1 (generally depicting a header made by Nico Pyrotechnic of Trittau, Germany), it is known to use two pins 25 raised above the glass (45)/metal (60) header surface, with xe2x80x9cnailheadsxe2x80x9d 26 on the ends of the pins 25, to help retain the droplet in place on the surface of the header. As shown by crack 27, however, after the liquid or slurry droplet 80 is dispensed and begins to harden, it tends to contract around the pins 25, creating a region between the pins 25 that is prone to cracking apart at crack 27. The effects of this are potentially magnified by the fact that such a crack may be immediately adjacent to the bridgewire 70. Further, in the plane of the nailheads of pins 25, a crack 28 may also form between the nailheads of the pins 25 and the edges of the droplet 80, potentially allowing the top of the droplet 80 to shear away from the rest of the droplet 80. Thus, there remains a need for improvement of the means of retaining such droplets in place on the header.
In accordance with the present invention, a header for an initiator is provided that includes a center pin with a circumferential notch retention feature. The circumferential notch retention feature of the center pin enhances secure and effective disposition of an ignition pyrotechnic charge droplet to the header in the area of the bridgewire.